Priscila Hasse Palharim

Bio: Priscila Hasse Palharim is an academic researcher from University of São Paulo. The author has contributed to research in topics: Photocatalysis & Irradiation. The author has an hindex of 2, co-authored 5 publications receiving 18 citations.

Comparison between UVA- and zero-valent iron-activated persulfate processes for degrading propylparaben.

Abstract: Conventional wastewater treatments are not efficient in removing parabens, which may thus end up in surface waters, posing a threat to aquatic biota and human health. As an alternative treatment, persulfate (PS)-driven advanced oxidation technologies have gained growing attention for removing these pollutants. In this study, the degradation of propylparaben (PrP) by UVA- and zero-valent iron (ZVI)-activated persulfate was investigated. The effects of initial PS concentration ([PS]0) and irradiance or ZVI concentration were explored using the Doehlert experimental design. For the UVA-activated system, the specific PrP degradation rate (k) and percent removal were consistently higher for increasing [PS]0 and irradiance, varying in the ranges 0.0053–0.0192 min−1 and 37.9–77.3%, respectively. In contrast, extremely fast PrP degradation was achieved through the ZVI/PS process (0.3304 < k < 0.9212 min−1), with removal percentages above 97.5%; in this case, paraben degradation was hindered for a ZVI dosage beyond 40 mg L−1. Regarding toxicity, ECOSAR predictions suggest that the degradation products elucidated by LC-MS/MS are less toxic than PrP toward fish, daphnid, and green algae. In addition, both processes showed to be strongly dependent on the water matrix, being ZVI/PS more impacted for a MBR effluent, although its performance was much better than that exhibited by the UVA-driven process (t1/2 of 65.4 and 276.1 min, respectively).

Effect of HCl and HNO3 on the synthesis of pure and silver-based WO3 for improved photocatalytic activity under sunlight

Abstract: Heterogeneous photocatalysis have been considered an important and efficient alternative water and wastewater treatment process. In this area, different semiconductors, such as tungsten trioxide, have been investigated aiming to enhance photocatalytic performance. WO3 is known to be an efficient material with high stability in acidic conditions. In the present work, pure and Ag/AgCl-doped WO3 photocatalysts were synthesized by a simple hydrothermal method. A discussion of the effects of two pH-controlling agents, HCl and HNO3, in the final properties of the catalyst is reported for the first time. The materials were characterized by XRD, BET, SEM, EDS and UV–vis DRS. All catalysts showed similar or enhanced band gap values compared to a standard photocatalyst benchmark (TiO2 P25). The type of acid did not lead to significant differences in morphology or photocatalytic activity of undoped catalysts. In contrast, doped catalysts prepared using HCl resulted in particles of flower-like morphology, with higher uniformity and slightly narrower band gap values. Furthermore, the use of HCl in the synthesis of silver-doped WO3 resulted in catalysts containing AgCl, while Ag0 was the major dopant species when HNO3 was used. All materials exhibited good photocatalytic activity, with a maximum of 75.4% acetaminophen degradation under simulated sunlight achieved by the catalyst prepared with HCl and doped with 5% Ag-equivalent. For this catalyst, the degradation kinetics was found to be consistent with the Langmuir-Hinshelwood (L−H) model, and reusability tests showed no significant decrease in the degradation efficiency after four cycles. Finally, the effects of different scavengers suggest that O2•− species play a major role in acetaminophen degradation with the material containing WO3, Ag and AgCl.

Enhancing the visible-light photoactivity of silica-supported TiO2 for the photocatalytic treatment of pharmaceuticals in water.

Abstract: Catalyst samples based on SiO2-supported TiO2 were prepared with the incorporation of Ag (metal), S (nonmetal), and ZnO@S (semiconductor and nonmetal). The materials were evaluated regarding their morphological, optical, and crystalline properties as well as their photoactivity under visible and ultraviolet light toward the degradation rate of a model emerging pollutant, acetaminophen (ACT). All modified materials exhibited improved performance over the undoped catalyst. The Ag-doped catalyst achieved the largest degradation under visible radiation (about 30% in 120 min), whereas under ultraviolet irradiation, the ZnO@S-doped sample exhibited the best performance (about 62% in 120 min). A Doehlert design was carried out to evaluate the influence of pH and temperature on the photoactivity of Ag-TiO2/SiO2. In addition, the role of each reactive species in the photodegradation reaction was investigated by radical scavenger experiments, and the superoxide radical anion O2•− was shown to be the predominant reactive species. The stability of the Ag-TiO2/SiO2 material under ultraviolet and visible light was confirmed after five successive operation cycles, showing a reasonable (about 50%) loss of activity under visible irradiation and a slight improvement (about 13%) under UV light, as a result of the photo-reduction of Ag+. Lastly, the effect of the initial pollutant concentration showed that ACT degradation using Ag-TiO2/SiO2 follows the Langmuir-Hinshelwood kinetics, with intrinsic reaction rate k = 2.71 × 10−4 mmol L−1 min−1 under visible-light radiation.

Effect of temperature and time on the hydrothermal synthesis of WO3-AgCl photocatalysts regarding photocatalytic activity

Abstract: Heterogeneous photocatalysis is an important and promising alternative for efficient water and wastewater treatment processes. The synthesis of composite materials has attracted attention due to their improved photocatalytic activity and stability. In the present work, composites made of WO 3 -AgCl were synthesized by a simple one-step hydrothermal method. The evaluation of the effects of reaction temperature and synthesis time for this composite is reported for the first time. The materials were characterized by XRD, SEM, TEM, EDS, BET, UV–vis DRS, XPS, EPR and PL. All photocatalysts showed broad-spectrum activity due to their strong absorption in the UV region and some absorption in the visible region. The morphology of the materials was highly influenced by the synthesis temperature and time, which affected the photocatalytic efficiency. All materials exhibited good photocatalytic activity under simulated sunlight, with maximum acetaminophen removal of 99.6% for the catalyst synthesized at 120 °C and 12 h. Stability tests showed considerable stability after four cycles. The main reactive species participating in the photodegradation reaction were found to be O 2 •- > h + ~ • OH. T h e heterojunction formed between AgCl and WO 3 plays an important role in the photocatalytic activity, especially when the AgCl surface is not completely covered by WO 3 . • A simple one-step hydrothermal synthesis of WO 3 -AgCl photocatalysts is proposed; • Temperature and synthesis time drive the growth and morphology of WO 3 and AgCl; • The WO 3 -AgCl heterojunction favors photogenerated electron-holes separation; • Acetaminophen photodegradation was driven by O 2 •- > h + ~ • OH under visible light; • High photocatalytic activity and stability under simulated sunlight was achieved.